The race for space tourism may be hotting up, but the practicalities of intergalactic travel have hit a new obstacle.

Adding to the current crop of health risks involved in space travel, new research suggests that it could be harmful for the brain because galactic cosmic radiation could cause Alzheimer's.

The earth's magnetic field generally protects the planet and people in low earth orbit from these cosmic radiation, but once astronauts leave orbit they are exposed to constant shower of various radioactive particles.

Exposure to radiation levels could speed up changes in the brain that are linked to Alzheimer's disease

Senior author of the study, Professor Kerry O'Banion from the University of Rochester Medical Centre (URMC) Department of Neurobiology and Anatomy said: 'Galactic cosmic radiation poses a significant threat to future astronauts.

'The possibility that radiation exposure in space may give rise to health problems such as cancer has long been recognised.

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'However, this study shows for the first time that exposure to radiation levels equivalent to a mission to Mars could produce cognitive problems and speed up changes in the brain that are associated with Alzheimer's disease.'

Tests on mice with models of Alzheimer's showed that after they were exposed to various doses of
radiation, including levels comparable to what astronauts would be
experience during a mission to Mars, they were far more likely to fail these
tasks - suggesting neurological impairment - earlier than these symptoms
would typically appear.

The brains of the mice also showed
signs of vascular alterations and a greater than normal accumulation the
protein 'plaque' that accumulates in the brain and is one of the
hallmarks of the disease.

'These findings clearly suggest that
exposure to radiation in space has the potential to accelerate the
development of Alzheimer's disease,' said Professor O'Banion.

A diseased brain- showing the effects of dementia. Tests in mice showed those exposed to cosmic radiation displayed cognitive problems earlier in life

'This is yet another factor that
NASA, which is clearly concerned about the health risks to its
astronauts, will need to take into account as it plans future missions.'

With
appropriate warning, astronauts can be shielded from some forms of
radiation, but there are also other forms of cosmic radiation that
cannot be effectively blocked.

The
longer an astronaut is in deep space, the greater the exposure, which
could prove a worry for NASA as the agency is planning manned missions
to a distant asteroid in 2021 and to Mars in 2035.

The round trip to Mars could take as long as three years.

NASA has been funding research to determine the potential health risks of space travel for twenty-five years, in order to develop precautions and to determine if the risks warranted sending men and women on extended missions into deep space.

Several studies have demonstrated the potential cancer, cardiovascular, and musculoskeletal impact of galactic cosmic radiation but for the first time this study examines the potential impact of space radiation on neurodegeneration, in particular, the development of Alzheimer's disease.

The researchers, who have been working with NASA for eight years, studied the impact of a particular form of radiation called high-mass, high-charged (HZE) particles which are propelled through space at very high speeds by the force of exploding stars and come in many different forms.

For this study the researcher chose iron particles. Unlikely hydrogen protons, which are produced by solar flares, the mass of HZE particles like iron, combined with their speed, enable them to penetrate solid objects such as the wall and protective shielding of a spacecraft.

'Because iron particles pack a bigger wallop it is extremely difficult from an engineering perspective to effectively shield against them,' said Professor O'Banion.

'One would have to essentially wrap a spacecraft in a six-foot block of lead or concrete.'

A portion of the research was conducted at the NASA Space Radiation Laboratory which has particle accelerators which - by colliding matter together at very high speeds - can reproduce the radioactive particles found in space.